1. Field of the Invention
This invention relates generally to battery powered electronic devices, and more particularly, to systems for recharging and maintaining operation of such battery powered electronic devices.
2. Background Information There are a multitude of battery powered devices which are in wide-spread use today including laptop computers, cell phones, personal digital assistants (PDAs), walkie-talkies, cordless power tools, and mobile video and video game systems. These devices typically operate using a battery that is recharged when the device is not in use. Often, the battery is recharged by connecting either the device (or a battery pack for the device) into an external A/C source such as the typical 110 or 220-volt electrical outlet in the consumer's home or office. Many application devices also include an adapter that can connect to a D/C source such as an automobile lighter.
Other devices have been developed that allow a consumer to operate, or recharge, a mobile phone or laptop computer from a PC via a USB port or other electrical connector. Other devices have a solar powered battery charger or backup. Travel packs that can charge a battery by electrically connecting an alternating or direct current power source or a battery to a rechargeable battery have been developed. However, rechargeable batteries are typically kept charged and maintained with the device with which they are to be used, even where no alternating current or direct current sources are available to charge the application battery when it is discharged. This creates problems where the application device user is in traffic, or otherwise does not have access to another source of electricity. The opportunity to make a mobile telephone call, or to send Email messages, or use a PDA, for example, has been lost. The problem may be anything from a mere inconvenience to a life-threatening deficiency, depending on the particular circumstances in which the user finds themselves.
Furthermore, even though many application devices include rechargeable batteries, there is a time element required for a recharge, particularly a full recharge, of the application device batteries. Thus, even though an external power source may be available to recharge a battery, it may not be convenient or possible for the user to tether the device to that external power source at that time.
There are also devices which can provide power or recharge the battery in an application device that utilize a zinc/air fuel cell system that operates without an external power source. Such cells typically can be used for about three charges, or for a quick boost allowing device operation for a short period of time, e.g. one brief phone call or several short Email messages. The zinc/air fuel cells, however, begin to discharge immediately upon exposure to oxygen in the air. Thus, these devices must be kept sealed while not in use, and even then, air leakage into the cartridge can still cause a small, but continual discharge diminishing their effectiveness over time.
There remains a need for an electrical power system that can be used either to operate an application device and/or to recharge a battery in an application device that has the versatility to be used with a conventional electrical outlet, an automobile D/C current source, or an independent power source. It is further desirable if this device can accept a new source of fuel to provide power on an “as needed basis.” One way to meet these demands is to integrate into the device components that are capable of accepting alternating and/or direct currents to power an application device, as well as a direct oxidation fuel cell which is also capable of powering the application device or charging the battery associated with the application device.
Recently, there have been developments in direct oxidation fuel cell technology. Fuel cells are devices in which an electrochemical reaction is used to generate electricity. A variety of materials may be suitable for use as a fuel, depending upon the materials chosen for the components of the cell. The zinc air fuel cell mentioned previously is one example of a fuel cell. In the zinc air fuel cell, exposure to air begins the chemical reaction that is used to generate electricity.
Other organic materials such as methanol or natural gas are attractive choices for fuel due to their high specific energy. Direct oxidation fuel cell systems use carbonaceous liquid fuel in an aqueous solution (typically aqueous methanol), which is applied to the anode face of a membrane electrode assembly (MEA). The MEA contains a protonically conductive but, electronically non-conductive membrane (PCM), typically a catalyst which enables direct oxidation of the fuel on the anode is disposed on one surface of the PCM or is otherwise present in the anode chamber of the fuel cell. Upon exposure of the PCM to the methanol solution, protons (from hydrogen found in the fuel) and water molecules create an anodic reaction, thus separating the protons from the electrons. The protons migrate through the PCM, which is impermeable to the electrons. The electrons thus seek a different path to reunite with the protons and oxygen molecules involved in the cathodic reaction and travel through a load, providing electrical power.
This reaction begins when the fuel is introduced into the anode chamber and comes in contact with the anode face of the PCM. The reaction continues as the fuel substance is consumed. Thus, the reaction can be stopped when the fuel is no longer introduced into the anode chamber or upon separation of the fuel delivery source from the fuel cell. Thus, the cell does not continue to provide electricity unless fuel is introduced into the anode chamber.
There remains a further need for such a device that has an independent power source that involves an electricity generating reaction which proceeds and produces electricity when the electricity is needed, and does not discharge or continue producing power when it is not needed.
It is thus an object of the present invention to provide a versatile power system for providing power to an application device (or a battery for an application device) that can be used either with an A/C external source, a D/C external source or an independent power cell, and which does not depend on external environmental factors to operate effectively.